Ingredients

• 1 tablespoon olive oil
• 1 tablespoon unsalted butter
• 1 fennel bulb, trimmed and chopped
• 1 small onion, chopped
• 1 pound mixed dark leafy greens such as collard and beet, coarse stems and center ribs discarded and leaves chopped
• 6 cups water
• 3 cups baby spinach (2 ounces)
• 1/2 cup heavy cream
• 1 tablespoon fresh lemon juice
• Garnish: fennel fronds or chopped dill

Instructions

1. Heat oil and butter in a 6-quart heavy pot over medium heat until foam subsides. Add fennel, onion, 3/4 teaspoon salt, and 1/8 teaspoon pepper and cook, stirring occasionally, until softened and lightly browned, 7 to 8 minutes.
2. Add leafy greens (but not spinach) and water to pot and simmer, covered, until greens are tender, about 30 minutes. Stir in spinach and cook, uncovered, just until wilted, about 1 minute.
3. Purée soup in batches in a blender (use caution when blending hot liquids) until smooth, then return to pot. Stir in cream and lemon juice and reheat over low heat. Season with salt.
4. Cooks' note: Soup can be made 2 days ahead and chilled (covered once cool). Reheat or serve cold.
5. Soup can be made 2 days ahead and chilled (covered once cool). Reheat or serve cold.